Powdery molybdenum oxysulfide dithiocarbamate composition, a process for producing same, and a grease composition containing the composition

ABSTRACT

A grease composition comprising 0.1 to 10 parts by weight of a powdered molybdenum oxysulfide dithiocarbamate composition which comprises a compound represented by the following formula: ##STR1## wherein R 1 , R 2 , R 3  and R 4  are independent hydrocarbyl groups and may be the same or different groups, and the total number of carbon atoms contained in R 1  to R 4  is 4 to 36; and wherein X is sulfur or oxygen and the composition of the total of all Xs is given as S m  and O n  in which m and n satisfy the ranges of 1.7≦m≦3.5 and 0.5≦n≦2.3, respectively, in which the constituent particles have diameters of not larger than 50 μm, based on 100 parts by weight of a base grease.

This is a continuation-in-part of application Ser. No. 08/284,128 filed on Aug. 2, 1994, now U.S. Pat. No. 5,494,608.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a powdery molybdenum oxysulfide dithiocarbamate composition, a process for producing same and a grease composition containing the composition. More specifically, the present invention relates to a powdery molybdenum oxysulfide dithiocarbamate composition which exhibits low corrosive action and has excellent lubricating properties, a process for producing it and a grease composition containing the composition.

2. Description of the Related Art

Heretofore, adding molybdenum oxysulfide dithiocarbamate to grease has been tried in order to improve extreme pressure properties, friction modifier properties and anti-wear properties of grease. Various methods for producing such molybdenum oxysulfide dithiocarbamate have been disclosed. For example, Japanese Patent Publication No.45-24562 discloses a method by which a compound having the general formula:

    [R.sub.2 N-CS-S].sub.2 Mo.sub.2 O.sub.m S.sub.n

(wherein m+n=4, m=2.35-3, n=1.65-1, and R is a hydrocarbyl group having 1 to 24 carbon atoms) can be produced by reacting together a secondary amine, carbon disulfide and molybdenum trioxide.

Japanese Patent Laid-Open No. 48-56202 discloses a method in which a compound represented by the following general formula: ##STR2## (wherein R is an alkyl group) can be produced by reacting the product given by the method of Japanese Patent Publication No. 45-24562 described above with phosphorus pentasulfide.

In addition, Japanese Patent Laid-Open Nos. 52-19629 and 52-106824 disclose methods by which a compound represented by the following general formula: ##STR3## (wherein R₅ and R₆ are independently hydrocarbyl groups having 1 to 24 carbon atoms. l is a number from 0.5 to 2.3, o is a number from 3.5 to 1.7 and l+o=4) can be produced by reacting carbon disulfide with a secondary amine in an aqueous solution or suspension containing molybdenum trioxide or an alkali metal salt or an ammonium salt of molybdic acid and an alkali hydrogensulfide or an alkali sulfide in a molar ratio of 1:0.05-4.

However, the compound of Japanese Patent Publication No. 45-24562 above is inferior in heat resistance and, in the grease preparation process, may cause a color change in the resulting grease. On the other hand, the compound described in Japanese Patent Laid-Open No. 48-56202 exhibits corrosive action against copper plates, thus the use of the compound has been limited. The compound described in Japanese Patent Laid-Open Nos.52-19629 and 52-106824 also still has room for improvement in terms of lubricating properties and corrosive properties. That is, when the powdery molybdenum oxysulfide dithiocarbamate is added to the grease to prepare a grease composition, its physical properties such as particle size have been neglected. As a result, the grease composition produced is not imparted with sufficient lubricating properties, and furthermore may cause slight vibrations.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a powdery molybdenum oxysulfide dithiocarbamate composition which, when used for a grease composition, exhibits excellent wear and friction properties and, therefore, exhibits excellent lubricating properties, as well as decreased corrosive action.

Another object of the present invention is to provide a process for effective production of the powdery molybdenum oxysulfide dithiocarbamate composition described above.

A further object of the present invention is to provide a grease composition which exhibits excellent wear and friction properties and therefore, exhibits excellent lubricity properties, as well as less corrosive action.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have carried out extensive research on various kinds of purified molybdenum oxysulfide dithiocarbamate from the viewpoint of corrosive action and lubricating properties. As a result, they have found a component effective for use as an additive for a grease composition and a process for producing the component, thereby attaining the present invention.

That is, according to the present invention, a powdery molybdenum oxysulfide dithiocarbamate composition can be provided which comprises a compound represented by the following general formula (1): ##STR4## (wherein R¹, R², R³ and R⁴ are independent hydrocarbyl groups and may be the same or different groups, and the total number of carbon atoms contained in R¹ to R⁴ is 4 to 36; and wherein X is sulfur or oxygen and the composition of the total of all Xs is given as S_(m) O_(n) in which m and n satisfy the ranges of 1.7≦m≦3.5 and 0.5≦n≦2.3, respectively). and in which constituent particles have diameters of not larger than 50 μm.

The powdery molybdenum oxysulfide dithiocarbamate composition according to the present invention can be produced by a process characterized in that:

(A) an aqueous solution or suspension prepared by reacting (a) molybdenum trioxide or an alkali metal salt or ammonium salt of molybdic acid with (b) alkali hydrogensulfide or alkali sulfide in a molar ratio of (a):(b)=1:1 to 1:2,

(B) carbon disulfide,

(C) secondary amine and

(D) mineral acid

are reacted together, wherein the molar ratio of (A), (B) and (C) is (A):(B):(C)=1:0.9-2:0.9-2 and the amount of (D) to be added is within the range satisfying the following equation (1):

    1-[(R'/4)+1]×1/10≦d≦1

[wherein R' is the total number of carbon atoms contained in R¹, R², R³ and R⁴ in formula (1) and d is the equivalent number of the alkali in the mineral acid as opposed to the alkali present in (A)] when the alkali equivalent in (A) is defined as 1, whereby a solid reaction product is obtained;

the resulting reaction product is slurried with an organic solvent; and

then the resulting slurry is washed, dried and powdered.

The grease composition of the present invention is characterized by containing 0.1 to 10 parts by weight of a powdery molybdenum oxysulfide dithiocarbamate composition which comprises a compound represented by the following general formula (1): ##STR5## (wherein R¹, R², R³, R⁴, X, m and n are the same as defined above), and of in which constituent particles have diameters of not larger than 50 μm, based on 100 parts by weight of a base grease.

In the compound of formula (1) to be used in the present invention, the hydrocarbyl groups represented by R¹, R², R³ and R⁴ may be saturated or contain unsaturated bond(s), may be straight chains, branched chains or cyclic chains or any combined form thereof, and may be the same or different. However, the total number of carbon atoms contained in R¹, R², R³ and R⁴ should be 4 to 36, preferably 4 to 32, and more preferably 8 to 32. When the total number is greater than the range above, the compound exhibits a lower melting point and therefore may become viscous at ordinary temperatures, resulting in poor handling, which is not desirable.

As such hydrocarbyl groups, aliphatic, aromatic and aromatic-aliphatic groups can be employed. Typical examples of such hydrocarbyl groups include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, octyl, 2-ethylhexyl, nonyl, decyl, lauryl, tridecyl, isotridecyl, myristyl, palmityl and stearyl; alkenyl groups such as propenyl, butenyl, isobutenyl, pentenyl, 2-ethylhexenyl, octenyl, oleyl and palmitoleyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, methylcyclohexyl and ethylcyclopentyl; aryl groups such as phenyl, naphthyl and alkyl substituent phenyl; aralkyl groups such as benzyl and phenethyl; and so on. Among these, preferably used are ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl and the like.

In the compound of formula (1), X is sulfur or oxygen, and the composition of the total of all Xs is given as S_(m) O_(n) wherein m satisfies the range of 1.7≦m≦3.5 and preferably 1.8≦m≦3.0 and n satisfies the range of 0.5≦n≦2.3 and preferably 1.0≦n≦2.2. When m is higher than the above range (i.e. n is lower than the above range), the compound exhibits undesirable corrosive properties. On the other hand, when m is lower than the above range (i.e n is higher than the range above), the compound exhibits poor lubricating properties. For these reasons, values of m and n which lie outside of the above range are not preferable.

In the molybdenum oxysulfide dithiocarbamate composition of the present invention which comprises a compound represented by formula (1), the constituent particles, i.e. the molybdenum oxysulfide dithiocarbamate particles, have diameters of not larger than 50 μm. Preferably, the composition contains particles of molybdenum oxysulfide dithiocarbamate of not smaller than 40 to not larger than 50 μm in diameter in an amount of not more than 5% by weight and particles of smaller than 40 μm in diameter in an amount of not less than 95% by weight, based on the total weight of the particles. Furthermore, in the molybdenum oxysulfide dithiocarbamate composition, it is most preferable that the average diameter of all of the particles is not larger than 20 μm in addition to the conditions described above.

An increase in particle diameter of the powdery molybdenum oxysulfide dithiocarbamate may cause not only a decrease in dispersibility in grease but also less effective lubricating properties thereof. For these reasons, the molybdenum oxysulfide dithiocarbamate particles which compose the powdery molybdenum oxysulfide dithiocarbamate composition of the present invention should have particle diameters of not larger than 50 μm.

Such powdery molybdenum oxysulfide dithiocarbamate compositions may be produced by synthesizing a molybdenum oxysulfide dithiocarbamate composition according to a conventional process known and then sieving the resultant composition. However, the composition can be prepared more effectively according to the process described below.

That is, the powdery molybdenum oxysulfide dithiocarbamate composition can be produced according to a process in which:

(A) an aqueous solution or suspension prepared by reacting (a) molybdenum trioxide or an alkali metal salt or ammonium salt of molybdic acid with (b) alkali hydrogensulfide or alkali sulfide in a molar ratio of (a):(b)=1:1 to 1:2,

(B) carbon disulfide.

(C) secondary amine and

(D) mineral acid are reacted together, wherein the reaction molar ratio of (A), (B) and (C) is (A):(B):(C)=1:0.9-2:0.9-2 and the amount of (D) to be added is within the range satisfying the following equation (1):

    1-[(R'/4)+1]×1/10≦d≦1

[wherein R' is the total number of carbon atoms contained in R¹, R², R³ and R⁴ in the formula (1) and d is the equivalent number of the mineral acid against the alkali present in (A)] when the alkali equivalent in (A) is defined as 1, to give a solid reaction product:

the resulting reaction product is slurried with an organic solvent; and

then the resulting slurry is washed, dried and powdered.

As the alkali metal salt and ammonium salt of the molybdic acid to be used as component (a) in the process above, conventionally employed are sodium molybdate, potassium molybdate, ammonium molybdate and the like.

As the alkali hydrogensulfide to be used as component (b), sodium hydrogensulfide, potassium hydrogensulfide and the like can be employed in flake form or as an aqueous solution. However, from the viewpoint of reactivity with solid molybdenum trioxide, an aqueous alkali hydrogensulfide solution is preferable.

As the alkali sulfides to be used as component (b), conventionally employed are sodium sulfide, potassium sulfide, ammonium sulfide and the like. In addition, an aqueous alkali sulfide solution can also be employed which is prepared by introducing a sulfurizing gas into an aqueous alkali hydroxide solution. However, from the viewpoint of corrosive action of the resulting product, it is preferable to use a solid such as sodium sulfide, potassium sulfide, ammonium sulfide or the like.

In the process for preparation of the molybdenum oxysulfide dithiocarbamate composition of the present invention, (a) molybdenum trioxide or an alkali metal salt or ammonium salt of molybdic acid [hereinafter, simply referred to as "(a) molybdenum trioxide etc."] must be reacted at least partially, preferably more than 50 mole %, and more preferably more than 80 mole %, with (b) alkali hydrogensulfide or alkali sulfide [hereinafter, simply referred to as "(b) alkali hydrogensulfide etc."], prior to the reaction with (C) secondary amine, (B) carbon disulfide and (D) mineral acid. If component (a) is not at all initially reacted with component (b). a large amount of by-products may indesirably produced in the subsequent reaction with the components (B), (C) and (D). The reaction between components (a) and (b) can be almost entirely completed within 30 to 60 minutes by stirring at from an ordinary temperature to 60° C.

The molar ratio between (a) molybdenum trioxide etc. and (b) alkali hydrogensulfide etc. is a factor for determination of the composition of Xs in formula (1). The ratio should be 1.0 to 2.0 moles, preferably 1.2 to 1.9 moles of (b) alkali hydrogensulfide etc. based on 1 mole of (a) molybdenum trioxide etc. A smaller ratio of (b) alkali hydrogensulfide etc. than the above range may cause the production of a large amount of isomers as Xs in formula (1) which contain a great deal of oxygen, thus resulting in poor lubricating properties of the composition, which is not preferable. On the other hand, a larger ratio of (b) alkali hydrogensulfide etc. than the above range may cause the production of a large amount of isomers as Xs in the general formula (1) which contain a great deal of sulfur, thus resulting in higher corrosive action of the composition, which is also not preferable.

In the present invention, (a) molybdenum trioxide etc. and (b) alkali hydrogensulfide etc. may be used in a solid form, aqueous solution or suspension or the like, so long as the reaction system contains water at least at the point when the reaction between (a) and (b) is carried out. For example, at least either of the components (a) or (b) is mixed in as an aqueous solution or suspension with the other, or both of the components are mixed in as solids and then water is added to the solid mixture to give an aqueous mixture solution or suspension to be then reacted. The reactant thus prepared is "(A) an aqueous solution or suspension".

Also, in the step of preparing (A) an aqueous solution or suspension by reacting (a) molybdenum trioxide etc. with (b) alkali hydrogensulfide etc., an organic solvent may be added to the reaction system before and/or during and/or after the reaction in a desired amount within a range which does not inhibit the reaction. As the thus used organic solvent, the same as those used in the slurrying step described below can be employed. However, this organic solvent is separate from that used in the slurrying step, and therefore is not taken into account as part of the total organic solvent used in slurrying step below.

In the secondary amine (C) to be used, the hydrocarbyl substituent groups may be saturated or contain unsaturated bond(s), and may be straight chains, branched chains or cyclic chains or any combined form thereof, and may be the same or different. As such hydrocarbyl groups, aliphatic, aromatic and aromatic-aliphatic hydrocarbyl groups can be employed. Typical examples of such hydrocarbyl groups include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, octyl, 2-ethylhexyl, nonyl, decyl, lauryl, tridecyl, isotridecyl, myristyl, palmityl and stearyl; alkenyl groups such as propenyl, butenyl, isobutenyl, pentenyl, 2-ethylhexenyl, octenyl, oleyl and palmitoyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, methylcyclohexyl and ethylcyclopentyl; aryl groups such as phenyl, naphthyl and alkyl-substituted phenyl; aralkyl groups such as benzyl and phenethyl; and so on. It is preferable to use one or more types of secondary amines substituted with one or more of the hydrocarbyl groups selected from ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl and so on.

As the mineral acid (D) to be used in the process described above, one or more kinds of acids other than organic acids selected from monobasic acids (e.g. hydrochloric acid, nitric acid, etc.), dibasic acids (e.g. sulfuric acid, etc.) and tribasic acid (e.g. phosphoric acid, etc.) and partially neutralized acids thereof max be employed.

In the process described above, any reaction order for components (A), (B), (C) and (D) can be employed. However, from the viewpoint of not producing by-products, the reaction order in which the components (B) and (C) are added simultaneously is preferable. More specifically, the reaction order preferably employed is one in which the components (B) and (C) are initially added to component (A) simultaneously and then component (D) is added to the resultant mixture, or in which the component (D) is initially added to the component (A) and then the components (B) and (C) are added to the resultant mixture simultaneously.

The molar ratio of (A) an aqueous molybdenum solution etc.: (C) a secondary amine: (B) carbon disulfide influences the production of by-products of the intended product. Therefore, the molar ratio of (A):(C):(B) to be employed is 1:0.9-2:0.9-2, and preferably 1:1-1.5:1-1.5, by which the by-product content in the product decreases.

The amount of the component (D) to be added should satisfy the following equation (1):

    1-[(R'/4)+1]×1/10≦d≦1

(wherein R' and d have the same meaning as defined above) when the equivalent of alkali present in (A) is defined as 1. The amount of the component (D) to be added is closely related to the yield of by-products and the intended product. An increase in the amount of (D) added leads to a higher yield of by-products, whereas a decrease in the amount of (D) added leads to the lower yield of the intended product.

In the process described above, the components (A), (B), (C) and (D) can sufficiently react with one another at approximately room temperature. However, the reaction temperature to be employed is preferably from 40° to 140° C. and is especially preferable from 60° to 110° C. The reaction time is from about 2 to 15 hours.

According to the process described above, a solid reaction product in a water suspension can be obtained. By washing, purifying, powdering and finally sieving the solid reaction product, the powdery molybdenum oxysulfide dithiocarbamate composition of the present invention can be obtained. However, this process has the disadvantages that it is hard to powder the product well because of its solid form, and also that the trace amount of metal content and by-products contained in the resulting solid reaction product can not be readily removed.

Accordingly, in order to effectively produce the powdery molybdenum oxysulfide dithiocarbamate composition of the present invention which comprises the compound represented by formula (1) above, the solid reaction product obtained by the reaction described above is slurried with an organic solvent once before it is subjected to washing and powdering steps. Due to incorporating the slurrying step into the process, the metal contents and by-products contained in the reaction product are easily removed by washing and, furthermore, a high yield of a powdery molybdenum oxysulfide dithiocarbamate composition having a small particle size can be readily obtained without a sieving step.

As the organic solvent to be used for slurrying in the process of the present invention, any organic solvent can be employed so long as it is a volatile organic compound such as an aliphatic, aromatic and aliphatic-aromatic compound. Examples of such organic compounds include alkanes such as pentane, hexane, cyclohexane and cyclopentane; alcohols such as methanol, ethanol, 2-propanol, propanol, butanol and amyl alcohol; alkyl ethers such as diethyl ether and ethyl-propyl ether; aromatic compounds such as benzene, toluene and xylene; and other conventional organic solvents such as tetrahydrofuran, pyridine, carbon tetrachloride, chloroform and dimethyl sulfoxide. Among these, from the viewpoint of dispersibility of the reaction product, alcohols such as methanol, ethanol and 2-propanol and aromatic compounds such as benzene, toluene and xylene are preferable.

Any amount of such an organic solvent can be employed so long as the reaction product can be slurryed, for example within a range of from 0.1 to 10 times by weight, preferably from 0.3 to 3 times by weight, the weight of the molybdenum trioxide (a) charged. An organic solvent in an amount smaller than the above range can not disperse the reaction product sufficiently; also the organic solvent in an amount larger than the above range can not greatly improve the dispersion effect. In the contrary, it makes the removal step for the solvent troublesome: both results being not preferable.

The powdery molybdenum oxysulfide dithiocarbamate composition of the present invention, which comprises the compound represented by formula (1), can be produced by slurrying the reaction product as described above and, if required, then washing the resulting slurry with water or a suitable organic solvent, and finally drying and powdering.

The grease composition of the present invention can be obtained by using the powdery molybdenum oxysulfide dithiocarbamate composition produced above, wherein the composition is added to a base grease in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the base grease. The grease composition thus obtained exhibits less corrosive action and has excellent lubricating properties.

If the content of the molybdenum oxysulfide dithiocarbamate composition is less than the above described range, sufficient lubricating properties can not be imparted. On the other hand, even if the content of the composition is higher than the above range, the intended effects can not be further improved. For these reasons, too low or too high a content of the composition is not appropriate industrially.

The base grease to be used in the grease composition is, for example, a metallic soap grease, a metallic soap complex grease, an urea-based grease or a grease using organically treated clay (e.g. bentone grease), in which a mineral oil and/or a synthetic oil is used.

The grease composition of the present invention may be incorporated with an extreme pressure agent such as zinc dithiophosphate, a sulfur-phosphorous compound or molybdenum dithiophosphate, etc. and a solid lubricant such as molybdenum disulfide, graphite and ethylene tetrafluoride etc. In addition, if necessary, other conventional components may also be added to the grease composition as additives for grease, such as a rust preventative (e.g. N-N-trimethylenediaminedioleate, sorbitan monooleate, etc.), an antioxidant (e.g. dioctyl phenylamine, butyl hydroxytoluene, etc.), etc. in an amount within the range conventionally employed.

EXAMPLES

The present invention will be illustrated in more detail by the following examples. However, it is to be understood that the invention is not intended to be limited by the examples.

In the Examples and Comparative Examples, the samples synthesized in the following Synthesis Examples were used.

SYNTHESIS EXAMPLE 1

Into a glass reactor, 500 ml of water and 144 g (1 mole) of powdered molybdenum trioxide were suspended, and then 221 g (1.5 moles) of 38 wt %-aqueous sodium hydrogensulfide solution was added to the resulting suspension while stirring under closed conditions, followed by reaction for about 30 min. Subsequently, 260 g of toluene was added to the reaction mixture, and 146 g (1.2 moles) of 30 wt %-aqueous hydrochloric acid solution was further added thereto. After further adding 142 g (1.1 moles) of di-n-butylamine and 84 g (1.1 moles) of carbon disulfide at room temperature, the resulting mixture was stirred at room temperature for 30 minutes and then heated to 95° to 102° C. to be reacted for 4 hours. The resulting reaction product was filtered without slurrying, washed initially with 300 ml of toluene and then with 300 ml of water and dried, thereby obtaining 662 g (95% yield) of a solid reaction product of a compound having the following formula: ##STR6## wherein the composition of all Xs was S₂ O₂.

Subsequently, the solid thus obtained was finely powdered for 2 hours using a mill, whereby a yellow powder (Sample 1) was obtained.

Sample 1 was fractionated by sieving. As a result, a powder composed of particles having diameters of not smaller than 50 μm (Sample 2), a powder composed of particles having diameters of not smaller than 40 μm and smaller than 50 μm (Sample 3) and a powder composed of particles having diameters of smaller than 40 μm (Sample 4) were obtained.

SYNTHESIS EXAMPLE 2

Into a glass reactor, 300 ml of water and 144 g (1 mole) of powdered molybdenum trioxide were suspended, and then 221 g (1.5 moles) of 38 wt %-aqueous sodium hydrogensulfide solution was added to the resulting suspension while stirring under closed conditions followed by reaction for about 30 min. Subsequently, 260 g of methanol was added to the reaction mixture, and 91 g (0.75 mole) of 30 wt %-aqueous hydrochloric acid solution was further added thereto. After further adding 265 g (1.1 moles) of di-2-ethylhexylamine and 84 g (1.1 moles) of carbon disulfide at room temperature, the resulting mixture was stirred at room temperature for 30 minutes and then heated to 95° to 102° C. to be reacted for 4 hours. The reaction product was present in a methanol-water emulsion as aggigations. The reaction product was filtered without slurrying, washed initially with 300 ml of methanol and then with 300 ml of water and dried, thereby obtaining 648 g (95% yield) of a solid reaction product. Subsequently, the solid thus obtained was finely powdered for 2 hours using a mill, whereby a yellow powder (Sample 5) was obtained.

Sodium content and particle diameters of Samples 1 to 5 given by Synthesis Examples 1 and 2 are summarized in Table 1. In this evaluation of each sample, the sodium content was determined according to the ICP method after washing the sample, and the particle diameter was determined by laser diffusion using a microtrack particle size distribution analyzer after dispersing the sample in methanol.

                  TABLE 1                                                          ______________________________________                                         Sample No.        1      2      3    4    5                                    ______________________________________                                         Sodium content (ppm)                                                                             650    850    800  560  500                                  Particle size distribution (%)                                                 not smaller than 50 μm                                                                        18     100              16                                   40-50 μm       14            100       13                                   smaller than 40 μm                                                                            68                 100  71                                   Average particle diameter (μm)                                                                28.5   66.2   44.0 14.1 26.2                                 ______________________________________                                    

EXAMPLE 1 AND COMPARATIVE EXAMPLE 1

Samples 6 to 9 were prepared by using Samples 2 to 4 above in the blending ratio shown in Table 2. Samples 1 to 5 and Samples 6 to 9 thus prepared were tested for dispersibility in grease and the lubrication. The results are summarized in Table 3.

                  TABLE 2                                                          ______________________________________                                         Sample No.         6      7       8    9                                       ______________________________________                                         Blending ratio                                                                 Sample 2                   5%      5%                                          Sample 3            5%    10%          10%                                     Sample 4           95%    85%     95%  90%                                     Average particle diameter (μm)                                                                 15.6   19.7    16.7 17.1                                    ______________________________________                                    

                                      TABLE 3                                      __________________________________________________________________________                       Example 1           Comparative Example                      Sample No.        3    4    6    9    1    2    5    7    8                    __________________________________________________________________________     Dispersibility in grease test                                                  Number of aggregates                                                                             29   12   19   25   39   51   32   50   42                   SRV friction test                                                              Friction coefficient                                                                             0.098                                                                               0.085                                                                               0.092                                                                               0.095                                                                               0.105                                                                               0.105                                                                               0.104                                                                               0.105                                                                               0.104                (after 30 min.)                                                                Amplitude of friction coefficient                                                                0.018                                                                               0.010                                                                               0.015                                                                               0.018                                                                               0.025                                                                               0.025                                                                               0.021                                                                               0.022                                                                               0.023                (after 30 min.)                                                                __________________________________________________________________________

Dispersibility in Grease Test

Into a kneader, 100 parts by weight of a urea grease and 3 parts by weight of each sample were charged, and then mixed at 80° C. for 2 hours. Thereafter, the resulting grease mixture was applied on a glass plate in a thickness of about 1 mm, and then the dispersing state of the sample in the grease mixture was observed by means of a 20× reflection microscope. The dispersibility in grease of each sample was evaluated by counting the number of aggregations of the sample which were present within the 3 mm² on the plate.

Friction Test

The friction test was carried out by means of a SRV dynamic friction test machine under the following conditions. The friction properties of each sample were evaluated by reading the coefficient of friction given after 30 minutes and the deflection of the coefficient of friction caused by a slight vibration. In this test, the same grease mixtures were used as those used in the dispersion test above.

Test conditions:

Load: 50 N

Temperature: 50° C.

Test time: 60 min.

Amplitude: 1 mm

Frequency of amplitude: 50 times/sec.

SYNTHESIS EXAMPLE 3

Into a glass reactor, 500 ml of water and 144 g (1 mole) of powdered molybdenum trioxide were suspended, and then 221 g (1.5 moles) of 38 wt %-aqueous sodium hydrogensulfide solution was added to the resulting suspension while stirring under closed conditions and then reacted for about 30 min. Subsequently, 260 g of toluene was added to the reaction mixture, and 146 g (1.2 moles) of 30 wt %-aqueous hydrochloric acid solution was further added thereto. After further adding 142 g (1.1 moles) of di-n-butylamine and 84 g (1.1 moles) of carbon disulfide at room temperature, the resulting mixture was stirred at room temperature for 30 minutes, and then heated to 95° to 102° C. to be reacted for 4 hours. The reaction product was present in a toluene-water emulsion as aggregations. The emulsion containing the reaction product was slurryed by adding 86 g of toluene, and then filtered out. The resultant slurry was washed initially with 300 ml of toluene and then with 300 ml of water and dried, thereby obtaining 648 g (931 yield) of a solid reaction product. Subsequently, the solid thus obtained was finely powdered for 2 hours using a mill, whereby a yellow powder (Sample 10) was obtained. The sodium content and particle size distribution of Sample 10 are shown in Table 4.

In this process, the amount of toluene used for slurrying was 0.6 times by weight that of molybdenum trioxide, and the equivalent number of the mineral acid based on 1 equivalent of the alkali was 0.8.

SYNTHESIS EXAMPLE 4

Into a glass reactor, 500 ml of water and 144 g (1 mole) of powdered molybdenum trioxide suspended, and then 221 g (1.5 moles) of 38 wt %-aqueous sodium hydrogensulfide solution was added to the resulting suspension while stirring under closed conditions and then reacted for about 30 min. Subsequently, 91 g (0.75 moles) of 30 wt %-aqueous hydrochloric acid solution was further added to the reaction mixture. After further adding 265 g (1.1 moles) of di-2-ethylhexylamine and 84 g (1.1 moles) of carbon disulfide at room temperature, the resulting mixture was stirred at room temperature for 30 minutes, then heated to 95° to 102° C. and reacted for 6 hours. The resulting reaction solution was cooled to 40° C. to aggregate the reaction product, and then 86 g of methanol was added thereto to produce a slurry. The resulting slurry was filtered, washed initially with 300 ml of methanol and then with 300 ml of water and dried, thereby obtaining 857 g (93% yield) of a solid reaction product. Subsequently, the solid thus obtained was finely powdered for 2 hours using a mill, whereby a yellow powder (Sample 11) was obtained. The sodium content and particle size distribution of Sample 11 are also shown in Table 4.

In this process, the amount of methanol used for slurrying was 0.6 times by weight that of molybdenum trioxide, and the equivalent number of the mineral acid based on 1 equivalent of the alkali was 0.5.

                  TABLE 4                                                          ______________________________________                                         Sample No.        10     11     12   13   14                                   ______________________________________                                         Sodium content (ppm)                                                                             20     15     30   14   20                                   Particle size distribution (%)                                                 not smaller than 50 μm                                                                        0      0      0    0    0                                    40-50 μm       0      1      2    0    0                                    smaller than 40 μm                                                                            100    99     98   100  100                                  Average particle diameter (μm)                                                                6.0    10.1   13.0 7.2  8.9                                  ______________________________________                                    

As shown in Table 4 above, the two kinds of molybdenum oxysulfide dithiocarbamate produced by Synthesis Examples 3 and 4 had reduced sodium i.e. impurity contents, and comprised fine particles, as they were produced by a process in which a slurrying step was incorporated as described above.

SYNTHESIS EXAMPLE 5

Into a glass reactor, 200 ml of water and 206 g (1 mole) of powdered ammonium molybdate were suspended, and then 101 g (1.3 moles) of powdered sodium sulfide was added to the resulting suspension while stirring under closed conditions and then reacted for about 1 hour. Subsequently, 400 g of methanol was added to the reaction mixture. After further adding 313 g (1.3 moles) of di-2-ethylhexylamine and 91 g (1.2 moles) of carbon disulfide at room temperature, the resulting mixture was stirred at 60° C. for 1 hour. Thereafter, 120 g (0.4 mole) of 32 wt %-aqueous sulfuric acid solution was further added to the reaction mixture, and the resulting mixture was then heated to 75° to 85° C. and reacted for 4 hours. The resulting reaction solution was cooled to 40° C. to aggregate the reaction product, and then 175 g of methanol was added thereto to give a slurry. The resulting slurry was filtered, washed initially with 400 ml of water and then with 400 ml of methanol and dried, thereby obtaining 820 g (89% yield) of a solid reaction product. Subsequently, the solid thus obtained was finely powdered for 2 hours using a mill, whereby a yellow powder (Sample 12) was obtained. The sodium content and particle size distribution of Sample 12 are also shown in Table 4.

In this process, the amount of methanol used for slurrying was 0.85 times by weight that of molybdenum trioxide, and the equivalent number of the mineral acid based on I equivalent of the alkali was 0.3.

SYNTHESIS EXAMPLE 6

Into a glass reactor, 200 ml of water and 144 g (1 mole) of powdered molybdenum trioxide were suspended, and then 117 g (1.5 moles) of powdered sodium sulfide was added to the resulting suspension while stirring under closed conditions and then reacted for about 30 min. Subsequently, 260 g of methanol was added to the reaction mixture, and then 255 g (2.1 moles) of 30 wt %-aqueous hydrochloric acid solution was added thereto. After further adding 168 g (1.3 moles) of di-isobutylamine and 99 g (1.3 moles) of carbon disulfide at room temperature, the resulting mixture was stirred at room temperature for 30 minutes, and then heated to 75° to 85° C. to be reacted for 4 hours. The reaction product was present in a methanol-water solution as aggregations. The solution containing the reaction product was slurryed by adding 288 g of toluene, and then filtered. The resultant slurry was washed initially with 300 ml of toluene and then with 300 ml of water and dried, thereby obtaining 592 g (851 yield) of a solid reaction product. Subsequently, the solid thus obtained was finely powdered for 2 hours using a mill, whereby a yellow powder (Sample 13) was obtained. The sodium content and particle size distribution of Sample 13 are shown in Table 4.

In this process, the amount of toluene used for slurrying was 2 times by weight that of molybdenum trioxide, and the equivalent number of the mineral acid based on 1 equivalent of the alkali was 0.7.

SYNTHESIS EXAMPLE 7 (COMPARATIVE EXAMPLE)

Into a glass reactor, 500 ml of water and 144 g (1 mole) of powdered molybdenum trioxide were suspended, and then 221 g (1.5 moles) of 38 wt %-aqueous sodium hydrogensulfide solution was added to the resulting suspension while stirring under closed conditions and then reacted for about 30 minutes. Subsequently, 260 g of methanol and 255 g (2.1 moles) of 30 wt %-aqueous hydrochloric acid solution were added to the reaction mixture. After further adding 265 g (1.1 moles) of di-2-ethylhexylamine and 84 g (1.1 moles) of carbon disulfide at room temperature, the resulting mixture was stirred at room temperature for 30 minutes. Thereafter, the resulting mixture was then heated to 95° to 102° C. and reacted for 4 hours. The resulting reaction solution was cooled to 40° C. to aggregate the reaction product, and then 86 g of methanol was added thereto to produce a slurry. The resulting slurry was filtered, washed initially with 300 ml of methanol and then with 300 ml of water and dried, to obtain 903 g (98% yield) of a black solid reaction product. As the resulting solid contained a large amount of impurities, the solid was separated out on a chromatographic column to obtain 230 g (25% yield) of a yellow reaction product.

In this process, the amount of methanol used for slurrying was 0.6 times by weight that of molybdenum trioxide, and the equivalent number of the mineral acid based on 1 equivalent of the alkali was 1.4.

SYNTHESIS EXAMPLE 8 (COMPARATIVE EXAMPLE)

Into a glass reactor, 500 ml of water and 144 g (1 mole) of powdered molybdenum trioxide were suspended, and then 221 g (1.5 moles) of 38 wt %-aqueous sodium hydrogensulfide solution was added to the resulting suspension while stirring under closed conditions and was reacted for about 30 minutes. Subsequently, 260 g of toluene and then 36 g (0.3 moles) of 30 wt %-aqueous hydrochloric acid solution were added to the reaction mixture. After further adding 142 g (1.1 moles) of di-n-butylamine and 84 g (1.1 moles) of carbon disulfide at room temperature. the resulting mixture was stirred at room temperature for 30 min. Thereafter, the resulting mixture was heated to 95° to 102° C. and reacted for 4 hours. The reaction product was present in a toluene-water emulsion as aggregates. Said emulsion containing the reaction product was slurried by adding 86 g of toluene, and then filtered. The resultant product was washed initially with 300 ml of toluene and then with 300 ml of water and dried, thereby obtaining 140 g (20% yield) of a solid reaction product. Subsequently, the solid thus given was finely powdered for 2 hours using a mill, whereby a yellow powder was obtained.

In this process, the amount of toluene used for slurrying was 0.6 times by weight that of molybdenum trioxide, and the equivalent number of the mineral acid based on I equivalent of the alkali was 0.2.

SYNTHESIS EXAMPLE 9

The same procedures as Synthesis Example 4 were carried out except that di-n-octylamine (1.1 moles) was used instead of di-2-ethylhexylamine (1.1 moles). The sample obtained by this process is referred to as Sample 14. The sodium content and particle size distribution of Sample 14 are also shown in Table 4.

EXAMPLE 2

Dispersibility in grease tests and the lubrication tests were carried out on Sample 10 to 14. The results are summarized in Table 5.

                                      TABLE 5                                      __________________________________________________________________________                      Example 2                                                     Blending Sample No.                                                                             10  10  10   11  12   13  14                                  __________________________________________________________________________     Blending amount (%)                                                                             1   3   5    3   3    3   3                                   Dispersibility in grease test                                                  Number of aggregates                                                                            4   8   10   4   10   5   8                                   SVR friction test                                                              Friction coefficient                                                                            0.095                                                                              0.075                                                                              0.085                                                                               0.065                                                                              0.074                                                                               0.068                                                                              0.073                               (after 30 min.)                                                                Amplitude of friction coefficient                                                               0.015                                                                              0.008                                                                              0.012                                                                               0.004                                                                              0.010                                                                               0.006                                                                              0.009                               (after 30 min.)                                                                __________________________________________________________________________

Dispersibility in Grease Test

Into a kneader, 100 parts by weight of a urea grease and 3 parts by weight of each sample were charged, and then mixed at 80° C. for 2 hours. Thereafter, the resulting grease mixture was applied on a glass plate in a thickness of about 1 mm, and then the dispersing state of the sample in the grease mixture was observed by means of a 20× reflection microscope. The dispersibility in grease of each sample was evaluated by counting the number of aggregations of the sample which were present within the 3 mm² on the plate.

Friction test

The friction test was carried out by means of a SRV dynamic friction test machine under the following conditions. The friction property of each sample was evaluated by reading the coefficient of friction given after 30 minutes and the deflection of the coefficient of friction caused by a slight vibration. In this test, the same grease mixtures were used as those used in the dispersion test above.

Test conditions:

Load: 50 N

Temperature: 50° C.

Test time: 60 min.

Amplitude: 1 mm

Frequency of amplitude: 50 times/sec.

As described above, an effect of the present invention is that a powdery molybdenum oxysulfide dithiocarbamate composition can be provided which, when used for a grease composition, exhibits excellent wear and abrasive properties and, therefore, exhibits excellent lubricating properties, as well as decreased corrosive action.

Another effect of the present invention is that a process for effective production of the powdery molybdenum oxysulfide dithiocarbamate composition described above may be provided.

A further effect of the present invention is that a grease composition which exhibits excellent wear and abrasive properties and, therefore, exhibits excellent lubricating properties, as well as decreased corrosive action can be provided. That is, the grease composition of the present invention, which comprises a molybdenum oxysulfide dithiocarbamate composition having a ready dispersibility in a base grease, can exhibit excellent friction and abrasive properties and decreased corrosive action in a lubrication system, and therefore, can be used as a grease for all purposes such as in synchronized joints of automobiles.

Abrasion Resistance Test

To 100 parts by weight of urea grease, 3 parts by weight of each sample (inventive samples 3, 4, 6, 9-14, comparative samples 1, 2, 5, 7 and 8) was added in order to prepare test samples. For said test samples, the wear resistance test was carried out by using a Soda-type four-ball test employing a step-up method. The maximum friction coefficient at each load and the diameter (μm) of abrasion trace after each test were measured and the obtained results are shown in the following Tables.

Test conditions:

Load: 0.5-3 kg (the step-up method was carried out by adding 0.5 kg of load each time)

Test time: 1 min. per load (Total time=6 min.)

Rotating speed: 200 rpm

Temperature: 25° C.

Testing Ball: 3/4 inch ball (SUJ-2)

WORKING EXAMPLE

                                      TABLE 1                                      __________________________________________________________________________             Inventive Sample                                                       Load    3   4   6   9   10  11  12  13  14                                     __________________________________________________________________________     0.5 kg  0.043                                                                              0.045                                                                              0.043                                                                              0.045                                                                              0.043                                                                              0.045                                                                              0.043                                                                              0.045                                                                              0.044                                  1.0 kg  0.049                                                                              0.048                                                                              0.052                                                                              0.053                                                                              0.048                                                                              0.049                                                                              0.049                                                                              0.044                                                                              0.050                                  1.5 kg  0.055                                                                              0.049                                                                              0.048                                                                              0.052                                                                              0.049                                                                              0.050                                                                              0.048                                                                              0.050                                                                              0.048                                  2.0 kg  0.061                                                                              0.055                                                                              0.055                                                                              0.065                                                                              0.049                                                                              0.051                                                                              0.054                                                                              0.049                                                                              0.049                                  2.5 kg  0.076                                                                              0.056                                                                              0.046                                                                              0.078                                                                              0.049                                                                              0.051                                                                              0.052                                                                              0.051                                                                              0.051                                  3.0 kg  0.080                                                                              0.073                                                                              0.076                                                                              0.078                                                                              0.048                                                                              0.050                                                                              0.051                                                                              0.049                                                                              0.050                                  Diameter of                                                                            0.054                                                                              0.054                                                                              0.054                                                                              0.054                                                                              0.052                                                                              0.052                                                                              0.052                                                                              0.052                                                                              0.052                                  abrasion trace                                                                 __________________________________________________________________________

COMPARATIVE EXAMPLE

                  TABLE 2                                                          ______________________________________                                                  Comparative Sample                                                    Load       1        2      5      7    8                                       ______________________________________                                         0.5 kg     0.043    0.059  0.043  0.045                                                                               0.045                                   1.0 kg     0.077    0.086  0.074  0.075                                                                               0.072                                   1.5 kg     0.070    0.085  0.083  0.080                                                                               0.075                                   2.0 kg     0.086    0.074  0.075  0.076                                                                               0.080                                   2.5 kg     0.076    0.086  0.079  0.078                                                                               0.081                                   3.0 kg     0.081    0.088  0.081  0.081                                                                               0.080                                   Diameter of                                                                               0.056    0.057  0.056  0.056                                                                               0.056                                   abrasion trace                                                                 ______________________________________                                    

As can be seen from the above data, the Working Examples using the Inventive Samples 3, 4, 6, 9-14 with particle diameter not larger than 50 μm had better lubricity than the Comparative Examples using the Comparative Samples 1, 2, 5, 7 and 8. The friction coefficients at 1.0 kg (lead) for the Comparative Examples were more than 0.07, but the maximum friction coefficients for the Working Examples using the Inventive Samples 10-14 were about 0.05 and the friction coefficients for the Working Examples using the Inventive Samples 3 and 9 initially exceeded 0.07 at 2.5 kg (load). The above differences between the Working Examples and the Comparative Examples indicate the effects of specific diameter range of constituent particles. 

What is claimed is:
 1. A grease composition comprising: 0.1 to 10 parts by weight, based on 100 parts by weight of a base grease, of a powdered molybdenum oxysulfide dithiocarbamate composition which comprises a compound represented by the following formula: ##STR7## wherein R¹, R², R³ and R⁴ are independent hydrocarbyl groups and may be the same or different groups, and the total number of carbon atoms contained in R¹ to R⁴ is 4 to 36; and wherein X is sulfur or oxygen and the composition of the total of all Xs is given as S_(m) and O_(n) in which m and n satisfy the ranges of 1.8≦m≦3.0 and 1.0≦n≦2.2, respectively, in which the constituent particles have diameters of not larger than 50 μm.
 2. The grease composition according to claim 1, wherein the base grease is one selected from the group consisting of metallic soap greases, metallic soap complex greases, urea greases and greases using organically treated clay in which a mineral and/or a synthetic oil are used.
 3. The grease composition according to claim 1, which further comprises an extreme pressure agent, a solid lubricant, a rust preventative and/or an antioxidant.
 4. The grease composition according to claim 1, wherein the constituent particles are composed of not more than 5% by weight of particles having diameters of 40 to 50 μm and of not less than 95% by weight of particles having diameters of smaller than 40 μm based on the total weight of the composition.
 5. The grease composition according to claim 1, wherein the constituent particles have an average diameter of not larger than 20 μm. 